1. Field of the Invention
The present invention relates to a communication apparatus and a communication system.
2. Description of the Related Art
Data communication has recently become more and more important with the spreading Internet, etc. as its background. ATM networks in accordance with ITU-T I.150 have been introduced in this field to integrate telephony and data communication. High-speed optical communication network technologies such as SONET defined by ANSI T1.105, SDH defined by ITU-T G.707, and OTN defined by ITU-T G.872 have been introduced in this field. SONET and SDH have basically the same function, and OTN, an optical network, is based on the WOM (Wavelength Division Multiplexing) technology to raise the transmission capacity in a fiber.
These networks are interconnected by prescribing upper and lower layers based on the layer hierarchy of the OSI (Open System Interconnection) reference model defined by ISO. According to the provisions of these individual networks, ATM is ranked at the top; OTN, at the bottom; SONET and SDH, at the middle. Each network is also of hierarchic structure, consisting of subnetworks. For example, an ATM network consists of a virtual path and a virtual channel, and SONET/SDH and OTN are of hierarchic structures, consisting of subnetworks, as well.